This page made possible by the sponsorship of: Michael Collins.

Flagstaff
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flagstaff clear sky chart from 2005-11-06 to 2024-03-28.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
53%
24253
33%
79761
22%
24157
66%
24157
41%
38425

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
46%
754
37%
3990
22%
736
64%
736
27%
1699
January11th to 20thNight
45%
754
38%
3935
25%
740
61%
740
31%
1495
January21st to endNight
38%
830
22%
4273
20%
814
58%
814
19%
2339
February1st to 10thNight
43%
760
33%
2458
19%
760
63%
760
39%
1198
February11th to 20thNight
42%
740
34%
2219
22%
740
58%
740
39%
1137
February21st to endNight
38%
628
34%
1875
22%
628
54%
628
35%
992
March1st to 10thNight
35%
760
35%
2090
16%
760
55%
760
39%
1088
March11th to 20thNight
47%
760
33%
2090
19%
760
61%
760
41%
1139
March21st to endNight
39%
820
32%
2255
12%
820
58%
820
43%
1173
April1st to 10thNight
36%
720
31%
1980
11%
720
52%
720
42%
989
April11th to 20thNight
35%
574
37%
1814
15%
574
58%
574
40%
830
April21st to endNight
43%
540
44%
1620
19%
540
66%
540
49%
704
May1st to 10thNight
44%
540
37%
1620
20%
540
59%
540
50%
722
May11th to 20thNight
51%
531
39%
1594
23%
531
63%
531
52%
691
May21st to endNight
45%
582
34%
1746
18%
582
58%
582
51%
764
June1st to 10thNight
54%
540
35%
1620
25%
540
63%
540
59%
698
June11th to 20thNight
54%
540
36%
1620
25%
540
63%
540
65%
652
June21st to endNight
67%
540
33%
1620
26%
540
73%
540
62%
703
July1st to 10thNight
71%
525
25%
1575
20%
525
73%
525
45%
813
July11th to 20thNight
77%
522
21%
1566
18%
522
78%
522
43%
836
July21st to endNight
74%
591
18%
1674
17%
558
74%
558
32%
1012
August1st to 10thNight
78%
537
26%
1602
20%
534
79%
534
43%
827
August11th to 20thNight
79%
534
29%
1602
24%
534
80%
534
42%
847
August21st to endNight
81%
632
32%
1923
29%
632
82%
632
44%
1006
September1st to 10thNight
73%
720
29%
1980
24%
720
77%
720
46%
1071
September11th to 20thNight
75%
720
41%
1980
29%
720
83%
720
63%
932
September21st to endNight
68%
720
39%
1980
24%
720
78%
720
58%
933
October1st to 10thNight
57%
720
36%
2038
20%
720
70%
720
50%
1000
October11th to 20thNight
60%
720
41%
2160
27%
720
73%
720
59%
946
October21st to endNight
55%
792
44%
2376
27%
792
71%
792
54%
1042
November1st to 10thNight
54%
740
41%
2223
25%
740
71%
740
51%
1018
November11th to 20thNight
56%
760
40%
2470
27%
760
73%
760
53%
1029
November21st to endNight
47%
760
37%
2470
25%
760
64%
760
41%
1188
December1st to 10thNight
49%
760
35%
2470
24%
760
64%
760
39%
1215
December11th to 20thNight
46%
758
31%
2922
23%
758
60%
758
27%
1599
December21st to endNight
41%
829
21%
4331
21%
817
55%
817
22%
2098

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
342443445%7%58%
79269
Night
232332445%7%64%
80806
TransparencyDay
25%5%6%19%28%18%
78996
Night
21%46%20%29%20%
80601
SeeingDay
9%19%27%26%14%4
14034
Night
5%13%23%32%22%5%
24286

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
1236%5%3445%7%61%
2858
11th to 20thDay
14245%34346%63%
2860
21st to endDay
5%11%45%42345%6%51%
3146
February1st to 10thDay
16%345%1435%8%60%
1719
11th to 20thDay
16%345%2346%8%59%
1850
21st to endDay
15%35%5%35%46%6%57%
1579
March1st to 10thDay
16%233245%6%9%58%
2090
11th to 20thDay
27%35%434448%56%
2090
21st to endDay
242343345%9%60%
2256
April1st to 10thDay
232444445%8%61%
1980
11th to 20thDay
1324323347%68%
2090
21st to endDay
2423423347%66%
2340
May1st to 10thDay
2324434446%64%
2340
11th to 20thDay
23245%2446%6%63%
2301
21st to endDay
3323323346%68%
2530
June1st to 10thDay
2213323346%71%
2340
11th to 20thDay
21221223480%
2340
21st to endDay
222333445%5%66%
2340
July1st to 10thDay
4425%6%47%6%7%7%48%
2340
11th to 20thDay
6%5%36%7%6%8%9%8%10%33%
2340
21st to endDay
7%7%38%9%5%8%9%9%9%26%
2545
August1st to 10thDay
7%5%25%7%5%6%6%7%7%44%
2328
11th to 20thDay
5%5%36%7%5%8%8%8%8%38%
2299
21st to endDay
5%6%25%6%5%7%7%7%7%44%
2427
September1st to 10thDay
5%426%6%46%7%7%7%46%
1980
11th to 20thDay
331443335%6%64%
1980
21st to endDay
2323323348%66%
1980
October1st to 10thDay
4324423446%64%
1922
11th to 20thDay
331331223376%
1800
21st to endDay
2212222347%73%
1980
November1st to 10thDay
231222335%6%72%
1854
11th to 20thDay
1212322446%73%
1710
21st to endDay
3425%322326%67%
1710
December1st to 10thDay
36%2443335%7%59%
1710
11th to 20thDay
26%36%6%45%47%10%49%
2169
21st to endDay
46%36%5%345%5%7%51%
3146
January1st to 10thNight
1335%43446%8%61%
4097
11th to 20thNight
1325%32335%8%65%
4110
21st to endNight
5%8%35%5%345%6%5%52%
4521
February1st to 10thNight
15%2442335%7%64%
2458
11th to 20thNight
1333425%5%6%6%63%
2218
21st to endNight
15%25%42345%8%60%
1875
March1st to 10thNight
143332445%8%64%
2090
11th to 20thNight
26%432245%47%61%
2090
21st to endNight
241332446%8%64%
2255
April1st to 10thNight
1323322447%69%
1980
11th to 20thNight
1313224346%70%
1814
21st to endNight
11221235%6%76%
1620
May1st to 10thNight
121332335%7%71%
1620
11th to 20thNight
2212223346%75%
1594
21st to endNight
1212213345%75%
1746
June1st to 10thNight
2113212345%76%
1620
11th to 20thNight
111222122384%
1620
21st to endNight
1212313346%74%
1620
July1st to 10thNight
23135%35%6%6%9%57%
1620
11th to 20thNight
22135%36%7%7%10%52%
1620
21st to endNight
5%5%25%6%47%6%9%11%40%
1773
August1st to 10thNight
3313435%6%6%9%57%
1611
11th to 20thNight
3314436%6%7%13%50%
1602
21st to endNight
22235%35%5%7%9%57%
1923
September1st to 10thNight
33144345%7%8%56%
1980
11th to 20thNight
2212312345%74%
1980
21st to endNight
221221335%6%74%
1980
October1st to 10thNight
321332335%6%69%
2038
11th to 20thNight
231221223478%
2160
21st to endNight
2212212346%75%
2376
November1st to 10thNight
1312323445%72%
2223
11th to 20thNight
121222335%5%75%
2470
21st to endNight
2324324445%67%
2470
December1st to 10thNight
35%2332345%9%62%
2470
11th to 20thNight
26%35%435%5%5%8%53%
3041
21st to endNight
45%35%5%3445%5%56%
4521

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
25%36%24%30%11%
2859
11th to 20thDay
24%310%30%23%11%
2860
21st to endDay
35%3420%30%8%
3146
February1st to 10thDay
26%37%20%25%20%
1719
11th to 20thDay
25%45%23%25%18%
1860
21st to endDay
29%5%5%18%26%17%
1579
March1st to 10thDay
23%5%5%22%31%14%
2090
11th to 20thDay
27%5%5%21%30%12%
2090
21st to endDay
22%6%6%25%31%11%
2256
April1st to 10thDay
22%5%422%34%14%
1980
11th to 20thDay
18%3418%35%21%
2093
21st to endDay
21%4318%40%14%
2340
May1st to 10thDay
21%4418%37%16%
2340
11th to 20thDay
20%5%5%20%35%16%
2304
21st to endDay
18%3317%37%21%
2530
June1st to 10thDay
14%4213%33%33%
2340
11th to 20thDay
9%318%30%50%
2340
21st to endDay
18%4211%30%35%
2340
July1st to 10thDay
28%8%7%14%17%25%
2276
11th to 20thDay
39%9%15%16%13%8%
2271
21st to endDay
45%10%17%14%10%3
2404
August1st to 10thDay
35%7%11%14%17%16%
2313
11th to 20thDay
37%7%9%18%16%12%
2299
21st to endDay
34%8%9%18%24%8%
2427
September1st to 10thDay
32%7%9%14%18%20%
1980
11th to 20thDay
20%5%5%16%32%22%
1980
21st to endDay
19%4317%33%24%
1980
October1st to 10thDay
22%4420%24%26%
1922
11th to 20thDay
15%2312%34%34%
1800
21st to endDay
13%35%18%41%21%
1980
November1st to 10thDay
15%3427%33%18%
1854
11th to 20thDay
14%45%19%36%22%
1710
21st to endDay
22%2418%35%19%
1710
December1st to 10thDay
25%37%24%24%17%
1710
11th to 20thDay
34%38%21%22%12%
2168
21st to endDay
34%4420%25%12%
3146
January1st to 10thNight
24%4421%36%10%
4097
11th to 20thNight
21%38%31%27%10%
4110
21st to endNight
36%3418%29%10%
4521
February1st to 10thNight
22%36%20%27%21%
2458
11th to 20thNight
23%35%22%27%19%
2219
21st to endNight
24%5%417%31%18%
1875
March1st to 10thNight
20%5%5%22%35%13%
2090
11th to 20thNight
24%4424%31%12%
2090
21st to endNight
19%5%8%26%30%13%
2255
April1st to 10thNight
18%35%23%35%15%
1980
11th to 20thNight
17%3218%36%23%
1814
21st to endNight
12%3423%39%19%
1620
May1st to 10thNight
13%36%23%35%19%
1620
11th to 20thNight
12%3423%37%19%
1595
21st to endNight
13%3417%38%25%
1746
June1st to 10thNight
11%3212%34%37%
1620
11th to 20thNight
9%29%30%50%
1620
21st to endNight
13%239%27%45%
1620
July1st to 10thNight
22%7%10%13%19%30%
1575
11th to 20thNight
24%7%18%24%17%11%
1566
21st to endNight
33%8%21%20%12%5%
1674
August1st to 10thNight
23%6%15%18%20%19%
1602
11th to 20thNight
25%5%17%20%20%14%
1602
21st to endNight
22%7%10%25%26%11%
1923
September1st to 10thNight
24%5%10%18%24%19%
1980
11th to 20thNight
13%35%20%31%27%
1980
21st to endNight
13%3415%36%28%
1980
October1st to 10thNight
18%46%22%23%28%
2038
11th to 20thNight
13%2313%36%33%
2160
21st to endNight
12%3418%39%24%
2376
November1st to 10thNight
16%3424%35%19%
2223
11th to 20thNight
13%36%18%37%24%
2470
21st to endNight
22%3418%30%23%
2470
December1st to 10thNight
22%5%7%22%24%20%
2470
11th to 20thNight
31%46%19%25%15%
3041
21st to endNight
31%4420%22%20%
4521

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
8%26%34%21%10%1
270
11th to 20thDay
10%24%30%25%9%3
270
21st to endDay
7%26%30%23%13%1
297
February1st to 10thDay
15%23%27%24%10%1
279
11th to 20thDay
15%30%28%23%4
455
21st to endDay
20%31%30%15%41
382
March1st to 10thDay
19%30%29%17%5%
460
11th to 20thDay
15%25%29%20%8%2
460
21st to endDay
15%33%33%14%41
491
April1st to 10thDay
10%31%33%15%9%2
420
11th to 20thDay
14%33%30%15%6%1
412
21st to endDay
11%36%25%16%10%1
420
May1st to 10thDay
11%27%37%18%6%2
423
11th to 20thDay
6%25%32%22%10%4
448
21st to endDay
11%24%33%21%10%2
485
June1st to 10thDay
320%34%29%12%3
450
11th to 20thDay
5%18%36%25%12%4
450
21st to endDay
412%35%35%14%2
450
July1st to 10thDay
47%28%35%20%6%
446
11th to 20thDay
6%5%15%40%24%11%
444
21st to endDay
9%5%8%35%30%14%
487
August1st to 10thDay
7%419%37%24%9%
447
11th to 20thDay
4418%42%24%8%
437
21st to endDay
7%418%34%26%11%
495
September1st to 10thDay
8%7%22%33%22%8%
450
11th to 20thDay
5%10%32%29%19%5%
450
21st to endDay
7%14%25%31%18%6%
450
October1st to 10thDay
7%22%26%25%16%4
392
11th to 20thDay
7%17%23%27%19%7%
270
21st to endDay
9%21%25%25%16%3
297
November1st to 10thDay
11%17%27%28%14%3
270
11th to 20thDay
7%17%26%27%19%4
270
21st to endDay
12%21%26%23%13%4
270
December1st to 10thDay
12%18%31%24%13%2
270
11th to 20thDay
7%21%30%27%11%3
270
21st to endDay
18%19%30%25%6%1
297
January1st to 10thNight
7%16%25%29%16%6%
760
11th to 20thNight
8%14%27%29%17%6%
760
21st to endNight
9%19%28%29%13%3
836
February1st to 10thNight
6%19%28%29%15%3
760
11th to 20thNight
5%22%28%30%13%2
744
21st to endNight
10%22%28%28%10%1
628
March1st to 10thNight
9%24%28%28%10%2
760
11th to 20thNight
7%17%25%30%16%4
760
21st to endNight
6%20%31%29%12%1
820
April1st to 10thNight
424%30%28%12%2
720
11th to 20thNight
8%21%32%30%9%2
574
21st to endNight
422%29%27%15%3
540
May1st to 10thNight
418%31%35%11%1
540
11th to 20thNight
416%26%32%19%4
531
21st to endNight
5%16%30%29%18%2
584
June1st to 10thNight
211%29%40%16%1
540
11th to 20thNight
210%31%38%17%2
540
21st to endNight
3422%42%27%2
540
July1st to 10thNight
4114%39%38%4
525
11th to 20thNight
318%39%41%8%
522
21st to endNight
6%2431%47%10%
591
August1st to 10thNight
427%31%45%10%
537
11th to 20thNight
417%37%43%8%
534
21st to endNight
325%32%46%13%
632
September1st to 10thNight
448%30%45%9%
720
11th to 20thNight
3414%36%36%6%
720
21st to endNight
410%14%30%34%8%
720
October1st to 10thNight
5%11%22%36%23%3
720
11th to 20thNight
5%8%22%37%21%7%
720
21st to endNight
414%23%29%22%9%
792
November1st to 10thNight
414%24%32%21%4
740
11th to 20thNight
314%23%34%20%6%
760
21st to endNight
7%16%26%29%18%5%
760
December1st to 10thNight
9%15%24%29%21%2
760
11th to 20thNight
7%17%25%30%18%2
760
21st to endNight
9%15%29%32%11%4
836
Page generated at 2024-03-24 20:37:00. Version ac07

Copyright © 2024 Attilla Danko.


Flagstaff Clear Sky Chart |Charts Home